Broadly, the present invention relates to inhibition of chitinases.
Family 18 chitinases are found in a range of pathogenic organisms and also play a role in the pathophysiology of inflammation, such as lung inflammation and asthma.
Chitin, a polymer of β(1,4) linked N-acetylglucosamine (GlcNAc), is an essential structural component of fungal cell walls, the shells of nematode eggs and arthropod exoskeletons. Family 18 chitinases, which degrade this polymer, have recently been chemically and/or genetically validated as potential drug targets against pathogenic fungi [M. J. Kuranda and P. W. Robbins, Chitinase is required for cell-separation during growth of Saccharomyces cerevisiae, j. Biol. Chem., 266, 19758-19767 (1991); N. Takaya, D. Yamazaki, H. Horiuchi, A. Ohta, and M. Takagi, Cloning and characterisation or a chitinase-encoding gene chiA from Aspergillus nidulans, disruption of which decreases germination frequency and hyphal growth, Biosci.Biotechno.Biochem., 62, 60-65 (1998); and S. Sakuda. Studies on the chitinase inhibitors, allosamidins, volume 2 of Chitin Enzymology, pages 203-212. Atec Edizioni, 1996], nematodes [K. Arnold, L. J. Brydon, L. H. Chappell, and G. W. Gooday, Chitinolytic activities in heligmosomoides-polygyrus and their role in egg hatching, Mol.Biochem.Parasitol., 58, 317-323 (1993)], malaria transmission [J. M. Vinetz, J. G. Valenzuela, C. A. Specht, L. Aravind, R. C. Langer, J. M. C Ribeiro, and D. C. Kaslow, Chitinases of the avian malaria parasite Plasmodium gallinaceum, a class of enzymes necessary for parasite invasion of the mosquito midgut, J.Biol.Chem., 275, 10331-10341 (2000), and Y.-L. Tsai, R. E. Hayward, R. C. Langer, D. A. Fidock, and J. M. Vinetz, Disruption of Plasmodium falciparum chitinase markedly impairs parasite invasion of mosuito midgut, Infect.Immun., 69, 4048-4054 (2001)] and insects [S. Sakuda, A. Isogai, S. Matsumoto, A. Suzuki, and K. Koseki, The structure of allosamidin, a novel insect chitinase inhibitor produced by Streptomyces sp, Tetrahedron Lett., 27, 2475-2478 (1986); E. Cohen, Chitin synthesis and degradation as targets for pesticide action, Arch. insect Biochem. Physiol., 22, 245-261 (1993); K. Shiomi, N. Arai, Y. Iwai, A. Turberg, H. Koelbl, and S. Omura, Structure of argifin, a new chitinase inhibitor produced by Gliocladiun sp., Tetrahedron Lett., 41, 2141-2143 (2000); and N. Arai, K. Shiomi, Y Yamaguchi, R. Masuma, Y. wai, A. Turberg, H. Koelbl, and S. Omura, Argadin, a new chitinase inhibitor, produced by Clonostachys sp. FO-7314, Chem.Pharm.Bull., 48, 1442-1446 (2000)].
In addition, a recent study has shown that inhibition of a mammalian chitinase associated with parasitic infections reduces recruitment of inflammatory cells and profoundly dampens T helper 2 (Th2) cellular responses in a murine model of lung inflammation, suggesting this enzyme may be a potential target for an asthma drug therapy [Z. Zhu, T. Zheng, R. J. Horner, Y. K. Kim, N.Y. Chen, L. Cohn, Q. Hamid, and J. A. Elias, Acidic mammalian chitinase in asthmatic Th2 inflammation and IL-13 pathway activation, Science, 304, 1678-1682 (2004)].
Furthermore, chitinase-like lectins (chilectins), which are not enzymatically active appear to play a role in carbohydrate recognition and inflammation.
The enzymes have a conserved (β/α)8 fold, with a surface groove containing exposed aromatic residues, used for binding the chitin substrate. Family 18 chitinases employ an unusual reaction mechanism, where the acid protonating the glycosidic bond is a conserved glutamate and the nucleophile is the oxygen of the N-acetyl group on the −1 sugar, forming an oxazolinium ion intermediate. A range of chitinase inhibitors have been described, most of which are natural products. Allosamidin is a pseudotrisaccharide that mimics the oxazolinium reaction intermediate, inhibiting family 18 chitinases in the nM-μM range. Argifin, argadin and CI-4 are peptide-based inhibitors that mimic protein-carbohydrate interactions both in terms of hydrogen bonds and stacking interactions. Unfortunately, the currently available inhibitors have a number of properties that make them unsuitable as drug leads, including high molecular weights (e.g. allosamidin, argifin and argadini, several stereocenters, and low cLogP values (e.g. −5.2 for allosamidin). Additionally, such inhibitors are generally large, hydrophilic molecules which contain easily hydrolyzable chemical bonds, and are undesirable for therapeutic uses.
Therefore, there is a need to avoid or overcome the above mentioned disadvantages and provide molecules appropriate for therapy which interact with chitinase enzymes and/or chilectins.
There is also a need to provide molecules for the treatment of diseases such as pathogenic infections involving the synthesis and/or degradation of chitin.
There is also a need to provide molecules for use as anti-pathogenics, such as anti-fungal and anti-parasitic molecules.
There is also a need to provide molecules for use as insecticides.
There is also a need to provide molecules for the prevention or treatment of inflammatory disease.
There is also a need to provide molecules for the treatment of atherosclerosis and lipid storage disease.
Accordingly, the present invention seeks to meet one or more of the present needs.